Inhibin alpha beta heterodimers and beta beta homodimers are gonadal gene products important in the feedback regulation of pituitary FSH release, whereas fibroblast growth factor (FGF) and epidermal growth factor (EGF) are mitogens for diverse cell types. Recently, inhibins (alpha beta dimers), activins (beta beta dimers) and several growth factors have been shown to be important intragonadal hormones that are synthesized by the gonadal cells, have specific gonadal receptors and modulate specific genes in the ovary and testis. Following the purification and cloning of inhibin subunit genes, we have studied the expression, biosynthesis and action of inhibin and activin in gonadal cells. We have also demonstrated the regulation of gonadal steroidogenesis by basic FGF and EGF through specific receptors. We now continue out work 1) to study the regulation of inhibin alpha and beta antigens and message levels by trophic agents and steroids in granulosa cells and an equine granulosa cell tumor using RNA blotting, immunoblotting and RIA analysis, 2) to analyze tissue distribution as well as hormonal regulation of basic FGF and EGF message and antigen levels in granulosa, theca and luteal cells using reverse transcription-polymerase chain reaction, in situ hybridization, RNA blotting and immunoblotting, 3) to study the intraovarian actions of activin and growth factors by monitoring inhibin biosynthesis, oocyte maturation and an ovarian protease expression as well as by quantitating the regulation of receptor content for activin and basic FGF, 4) to study the hormonal regulation of the expression of inhibin subunits, EGF and basic FGF in testis cells and 5) to isolate mouse inhibin alpha and beta cDNA and the inhibin alpha gene in order to analyze DNA sequences involved in inhibin alpha subunit expression. The proposed studies should provide information on the role of inhibin-related proteins and the growth factors in intragonadal control mechanisms, serving as the basis for understanding the hormonal control of follicle maturation, ovulation, luteinization and gonadal differentiation.